[qtwayland] Fix url getting broken on openUrl. Contributes to JB#46776

UTF-8 string cannot be split in random position and assume getting
valid content on resulting parts. Switched chunk size to be based
on characters, encoded size will vary but don't think that should matter.

src/client/qwaylandwindowmanagerintegration.cpp

@@ -134,13 +134,13 @@ QByteArray QWaylandWindowManagerIntegration::desktopEnvironment() const
 void QWaylandWindowManagerIntegration::openUrl_helper(const QUrl &url)
 {
     if (isInitialized()) {
-        QByteArray data = url.toString().toUtf8();
+        QString data = url.toString();
 
         static const int chunkSize = 128;
         while (!data.isEmpty()) {
-            QByteArray chunk = data.left(chunkSize);
+            QString chunk = data.left(chunkSize);
             data = data.mid(chunkSize);
-            open_url(!data.isEmpty(), QString::fromUtf8(chunk));
+            open_url(!data.isEmpty(), chunk);
         }
     }
 }